Data centers have their roots in the huge computer rooms of the 1940s, typified by "ENIAC, one of the earliest examples of a data center. Early computer systems, complex to operate and maintain, required a special environment in which to operate. Many cables were necessary to connect all the components, and methods to accommodate and organize these were devised such as standard "racks to mount equipment, "raised floors, and "cable trays (installed overhead or under the elevated floor). A single "mainframe required a great deal of power, and had to be cooled to avoid overheating. Security became important – computers were expensive, and were often used for "military purposes. Basic design-guidelines for controlling access to the computer room were therefore devised.

During the boom of the microcomputer industry, and especially during the 1980s, users started to deploy computers everywhere, in many cases with little or no care about operating requirements. However, as "information technology (IT) "operations started to grow in complexity, organizations grew aware of the need to control IT resources. The advent of "Unix from the early 1970s led to the subsequent proliferation of freely available "Linux-compatible "PC operating-systems during the 1990s. These were called ""servers", as "timesharing "operating systems like Unix rely heavily on the "client-server model to facilitate sharing unique resources between multiple users. The availability of inexpensive "networking equipment, coupled with new standards for network "structured cabling, made it possible to use a hierarchical design that put the servers in a specific room inside the company. The use of the term "data center", as applied to specially designed computer rooms, started to gain popular recognition about this time.["citation needed]

The boom of data centers came during the "dot-com bubble of 1997–2000. "Companies needed fast "Internet connectivity and non-stop operation to deploy systems and to establish a presence on the Internet. Installing such equipment was not viable for many smaller companies. Many companies started building very large facilities, called Internet data centers (IDCs), which provide "commercial clients with a range of solutions for systems deployment and operation. New technologies and practices were designed to handle the scale and the operational requirements of such large-scale operations. These practices eventually migrated toward the private data centers, and were adopted largely because of their practical results. Data centers for cloud computing are called cloud data centers (CDCs). But nowadays, the division of these terms has almost disappeared and they are being integrated into a term "data center".

With an increase in the uptake of "cloud computing, business and government organizations scrutinize data centers to a higher degree in areas such as security, availability, environmental impact and adherence to standards. Standards documents from accredited "professional groups, such as the "Telecommunications Industry Association, specify the requirements for data-center design. Well-known operational metrics for "data-center availability can serve to evaluate the "commercial impact of a disruption. Development continues in operational practice, and also in environmentally-friendly data-center design. Data centers typically cost a lot to build and to maintain.["citation needed]

"IT operations are a crucial aspect of most organizational operations around the world. One of the main concerns is "business continuity; companies rely on their information systems to run their operations. If a system becomes unavailable, company operations may be impaired or stopped completely. It is necessary to provide a reliable infrastructure for IT operations, in order to minimize any chance of disruption. Information security is also a concern, and for this reason a data center has to offer a secure environment which minimizes the chances of a security breach. A data center must therefore keep high standards for assuring the integrity and functionality of its hosted computer environment. This is accomplished through redundancy of mechanical cooling and power systems (including emergency backup power generators) serving the data center along with fiber optic cables.

The "Telecommunications Industry Association's Telecommunications Infrastructure Standard for Data Centers[3] specifies the minimum requirements for telecommunications infrastructure of data centers and computer rooms including single tenant enterprise data centers and multi-tenant Internet hosting data centers. The topology proposed in this document is intended to be applicable to any size data center.[4]

Telcordia GR-3160, NEBS Requirements for Telecommunications Data Center Equipment and Spaces,[5] provides guidelines for data center spaces within telecommunications networks, and environmental requirements for the equipment intended for installation in those spaces. These criteria were developed jointly by Telcordia and industry representatives. They may be applied to data center spaces housing data processing or Information Technology (IT) equipment. The equipment may be used to:

Operate and manage a carrier's telecommunication network

Provide data center based applications directly to the carrier's customers

Provide hosted applications for a third party to provide services to their customers

Provide a combination of these and similar data center applications

Effective data center operation requires a balanced investment in both the facility and the housed equipment. The first step is to establish a baseline facility environment suitable for equipment installation. Standardization and modularity can yield savings and efficiencies in the design and construction of telecommunications data centers.

Standardization means integrated building and equipment engineering. Modularity has the benefits of scalability and easier growth, even when planning forecasts are less than optimal. For these reasons, telecommunications data centers should be planned in repetitive building blocks of equipment, and associated power and support (conditioning) equipment when practical. The use of dedicated centralized systems requires more accurate forecasts of future needs to prevent expensive over construction, or perhaps worse — under construction that fails to meet future needs.

The "lights-out" data center, also known as a darkened or a dark data center, is a data center that, ideally, has all but eliminated the need for direct access by personnel, except under extraordinary circumstances. Because of the lack of need for staff to enter the data center, it can be operated without lighting. All of the devices are accessed and managed by remote systems, with automation programs used to perform unattended operations. In addition to the energy savings, reduction in staffing costs and the ability to locate the site further from population centers, implementing a lights-out data center reduces the threat of malicious attacks upon the infrastructure.[6][7]

There is a trend to modernize data centers in order to take advantage of the performance and "energy efficiency increases of newer IT equipment and capabilities, such as "cloud computing. This process is also known as data center transformation.[8]

Organizations are experiencing rapid IT growth but their data centers are aging. Industry research company "International Data Corporation (IDC) puts the average age of a data center at nine years old.[8] "Gartner, another research company, says data centers older than seven years are obsolete.[9] The growth in data (163 zettabytes by 2025[10]) is one factor driving the need for data centers to modernize.

In May 2011, data center research organization "Uptime Institute reported that 36 percent of the large companies it surveyed expect to exhaust IT capacity within the next 18 months.[11]

Data center transformation takes a step-by-step approach through integrated projects carried out over time. This differs from a traditional method of data center upgrades that takes a serial and siloed approach.[12] The typical projects within a data center transformation initiative include standardization/consolidation, virtualization, "automation and security.

Standardization/consolidation: The purpose of this project is to reduce the number of data centers a large organization may have. This project also helps to reduce the number of hardware, software platforms, tools and processes within a data center. Organizations replace aging data center equipment with newer ones that provide increased capacity and performance. Computing, networking and management platforms are standardized so they are easier to manage.[13]

Virtualize: There is a trend to use IT virtualization technologies to replace or consolidate multiple data center equipment, such as servers. Virtualization helps to lower capital and operational expenses,[14] and reduce energy consumption.[15] Virtualization technologies are also used to create virtual desktops, which can then be hosted in data centers and rented out on a subscription basis.[16] Data released by investment bank Lazard Capital Markets reports that 48 percent of enterprise operations will be virtualized by 2012. Gartner views virtualization as a catalyst for modernization.[17]

Automating: Data center automation involves automating tasks such as "provisioning, configuration, "patching, release management and compliance. As enterprises suffer from few skilled IT workers,[13] automating tasks make data centers run more efficiently.

Securing: In modern data centers, the security of data on virtual systems is integrated with existing security of physical infrastructures.[18] The security of a modern data center must take into account physical security, network security, and data and user security.

The "Telecommunications Industry Association is a trade association accredited by ANSI (American National Standards Institute). In 2005 it published ANSI/TIA-942, Telecommunications Infrastructure Standard for Data Centers, which defined four levels of data centers in a thorough, quantifiable manner.[19] TIA-942 was amended in 2008, 2010, 2014 and 2017. TIA-942:Data Center Standards Overview describes the requirements for the data center infrastructure. The simplest is a Level 1 data center, which is basically a "server room, following basic guidelines for the installation of computer systems. The most stringent level is a Level 4 data center, which is designed to host the most mission critical computer systems, with fully redundant subsystems, the ability to continuously operate for an indefinite period of time during primary power outages.

The "Uptime Institute, a data center research and professional-services organization based in Seattle, WA defined what is commonly referred to today as "Tiers" or more accurately, the "Tier Standard". Uptime's Tier Standard levels describe the availability of data processing from the hardware at a location. The higher the Tier level, the greater the expected availability. The Uptime Institute Tier Standards are shown below.[20][21]

For the 2014 TIA-942 revision, the TIA organization and Uptime Institute mutually agreed["citation needed] that TIA would remove any use of the word "Tier" from their published TIA-942 specifications, reserving that terminology to be solely used by Uptime Institute to describe its system.

Other classifications exist as well. For instance, the German Datacenter Star Audit program uses an auditing process to certify five levels of "gratification" that affect data center criticality.

Uptime Institute's Tier Standards

Tier level

Requirements

I

Single non-redundant distribution path serving the critical loads

Non-redundant critical capacity components

II

Meets all Tier I requirements, in addition to:

Redundant critical capacity components

Critical capacity components must be able to be isolated and removed from service while still providing N capacity to the critical loads.

All IT equipment must be dual-powered provided with two redundant, distinct UPS feeders. Single-corded IT devices must use a Point of Use Transfer Switch to allow the device to receive power from and select between the two UPS feeders.

Each and every critical capacity component, distribution path and component of any critical system must be able to be fully compatible with the topology of a site's architecture isolated for planned events (replacement, maintenance, or upgrade) while still providing N capacity to the critical loads.

Onsite energy production systems (such as engine generator systems) must not have runtime limitations at the site conditions and design load.

Critical systems must be able to autonomously provide N capacity to the critical loads after any single fault or failure

Continuous Cooling is required for IT and UPS systems.

While any of the industry's data center resiliency systems were proposed at a time when availability was expressed as a theory, and a certain number of 'Nines' on the right side of the decimal point, it has generally been agreed that this approach was somewhat deceptive or too simplistic, so vendors today usually discuss availability in details that they can actually affect, and in much more specific terms. Hence, the leveling systems available today no longer define their results in percentages of uptime.

Note: The Uptime Institute also classifies the Tiers for each of the three phases of a data center, its design documents, the constructed facility and its ongoing operational sustainability.[22]

A data center can occupy one room of a building, one or more floors, or an entire building. Most of the equipment is often in the form of servers mounted in "19 inch rack cabinets, which are usually placed in single rows forming corridors (so-called aisles) between them. This allows people access to the front and rear of each cabinet. Servers differ greatly in size from "1U servers to large freestanding storage silos which occupy many square feet of floor space. Some equipment such as "mainframe computers and "storage devices are often as big as the racks themselves, and are placed alongside them. Very large data centers may use "shipping containers packed with 1,000 or more servers each;[23] when repairs or upgrades are needed, whole containers are replaced (rather than repairing individual servers).[24]

Design programming, also known as architectural programming, is the process of researching and making decisions to identify the scope of a design project.[25] Other than the architecture of the building itself there are three elements to design programming for data centers: facility topology design (space planning), engineering infrastructure design (mechanical systems such as cooling and electrical systems including power) and technology infrastructure design (cable plant). Each will be influenced by performance assessments and modelling to identify gaps pertaining to the owner's performance wishes of the facility over time.

Various vendors who provide data center design services define the steps of data center design slightly differently, but all address the same basic aspects as given below.

Modeling criteria are used to develop future-state scenarios for space, power, cooling, and costs in the data center.[26] The aim is to create a master plan with parameters such as number, size, location, topology, IT floor system layouts, and power and cooling technology and configurations. The purpose of this is to allow for efficient use of the existing mechanical and electrical systems and also growth in the existing data center without the need for developing new buildings and further upgrading of incoming power supply.

Design recommendations/plans generally follow the modelling criteria phase. The optimal technology infrastructure is identified and planning criteria are developed, such as critical power capacities, overall data center power requirements using an agreed upon PUE (power utilization efficiency), mechanical cooling capacities, kilowatts per cabinet, raised floor space, and the resiliency level for the facility.

Conceptual designs embody the design recommendations or plans and should take into account "what-if" scenarios to ensure all operational outcomes are met in order to future-proof the facility. Conceptual floor layouts should be driven by IT performance requirements as well as lifecycle costs associated with IT demand, energy efficiency, cost efficiency and availability. Future-proofing will also include expansion capabilities, often provided in modern data centers through modular designs. These allow for more raised floor space to be fitted out in the data center whilst utilising the existing major electrical plant of the facility.

Detailed design is undertaken once the appropriate conceptual design is determined, typically including a proof of concept. The detailed design phase should include the detailed architectural, structural, mechanical and electrical information and specification of the facility. At this stage development of facility schematics and construction documents as well as schematics and performance specification and specific detailing of all technology infrastructure, detailed "IT infrastructure design and IT infrastructure documentation are produced.

Mechanical engineering infrastructure design addresses mechanical systems involved in maintaining the interior environment of a data center, such as heating, ventilation and air conditioning (HVAC); humidification and dehumidification equipment; pressurization; and so on.[27] This stage of the design process should be aimed at saving space and costs, while ensuring business and reliability objectives are met as well as achieving PUE and green requirements.[28] Modern designs include modularizing and scaling IT loads, and making sure capital spending on the building construction is optimized.

Electrical Engineering infrastructure design is focused on designing electrical configurations that accommodate various reliability requirements and data center sizes. Aspects may include utility service planning; distribution, switching and bypass from power sources; uninterruptible power source (UPS) systems; and more.[27]

These designs should dovetail to energy standards and best practices while also meeting business objectives. Electrical configurations should be optimized and operationally compatible with the data center user's capabilities. Modern electrical design is modular and scalable,[29] and is available for low and medium voltage requirements as well as DC (direct current).

The higher the availability needs of a data center, the higher the capital and operational costs of building and managing it. Business needs should dictate the level of availability required and should be evaluated based on characterization of the criticality of IT systems estimated cost analyses from modeled scenarios. In other words, how can an appropriate level of availability best be met by design criteria to avoid financial and operational risks as a result of downtime? If the estimated cost of downtime within a specified time unit exceeds the amortized capital costs and operational expenses, a higher level of availability should be factored into the data center design. If the cost of avoiding downtime greatly exceeds the cost of downtime itself, a lower level of availability should be factored into the design.[31]

Aspects such as proximity to available power grids, telecommunications infrastructure, networking services, transportation lines and emergency services can affect costs, risk, security and other factors to be taken into consideration for data center design. Whilst a wide array of location factors are taken into account (e.g. flight paths, neighbouring uses, geological risks) access to suitable available power is often the longest lead time item. Location affects data center design also because the climatic conditions dictate what cooling technologies should be deployed. In turn this impacts uptime and the costs associated with cooling.[32] For example, the topology and the cost of managing a data center in a warm, humid climate will vary greatly from managing one in a cool, dry climate.

Modularity and flexibility are key elements in allowing for a data center to grow and change over time. Data center modules are pre-engineered, standardized building blocks that can be easily configured and moved as needed.[33]

A modular data center may consist of data center equipment contained within shipping containers or similar portable containers.[34] But it can also be described as a design style in which components of the data center are prefabricated and standardized so that they can be constructed, moved or added to quickly as needs change.[35]

The physical environment of a data center is rigorously controlled. "Air conditioning is used to control the temperature and humidity in the data center. "ASHRAE's "Thermal Guidelines for Data Processing Environments"[36] recommends a temperature range of 18–27 °C (64–81 °F), a dew point range of −9 to 15 °C (16 to 59 °F), and ideal relative humidity of 60%, with an allowable range of 40% to 60% for data center environments.[37] The temperature in a data center will naturally rise because the electrical power used heats the air. Unless the heat is removed, the ambient temperature will rise, resulting in electronic equipment malfunction. By controlling the air temperature, the server components at the board level are kept within the manufacturer's specified temperature/humidity range. Air conditioning systems help control "humidity by cooling the return space air below the "dew point. Too much humidity, and water may begin to "condense on internal components. In case of a dry atmosphere, ancillary humidification systems may add water vapor if the humidity is too low, which can result in "static electricity discharge problems which may damage components. Subterranean data centers may keep computer equipment cool while expending less energy than conventional designs.

Modern data centers try to use economizer cooling, where they use outside air to keep the data center cool. At least one data center (located in "Upstate New York) will cool servers using outside air during the winter. They do not use chillers/air conditioners, which creates potential energy savings in the millions.[38] Increasingly indirect air cooling is being deployed in data centers globally which has the advantage of more efficient cooling which lowers power consumption costs in the data center. Many newly constructed data centers are also using Indirect Evaporative Cooling (IDEC) units as well as other environmental features such as sea water to minimize the amount of energy needed to cool the space.

There are many types of commercially available floors that offer a wide range of structural strength and loading capabilities, depending on component construction and the materials used. The general types of "raised floors include stringer, stringerless, and structural platforms, all of which are discussed in detail in GR-2930 and summarized below.

Stringered raised floors - This type of raised floor generally consists of a vertical array of steel pedestal assemblies (each assembly is made up of a steel base plate, tubular upright, and a head) uniformly spaced on two-foot centers and mechanically fastened to the concrete floor. The steel pedestal head has a stud that is inserted into the pedestal upright and the overall height is adjustable with a leveling nut on the welded stud of the pedestal head.

Stringerless raised floors - One non-earthquake type of raised floor generally consists of an array of pedestals that provide the necessary height for routing cables and also serve to support each corner of the floor panels. With this type of floor, there may or may not be provisioning to mechanically fasten the floor panels to the pedestals. This stringerless type of system (having no mechanical attachments between the pedestal heads) provides maximum accessibility to the space under the floor. However, stringerless floors are significantly weaker than stringered raised floors in supporting lateral loads and are not recommended.

Structural platforms - One type of structural platform consists of members constructed of steel angles or channels that are welded or bolted together to form an integrated platform for supporting equipment. This design permits equipment to be fastened directly to the platform without the need for toggle bars or supplemental bracing. Structural platforms may or may not contain panels or stringers.

Data centers typically have "raised flooring made up of 60 cm (2 ft) removable square tiles. The trend is towards 80–100 cm (31–39 in) void to cater for better and uniform air distribution. These provide a "plenum for air to circulate below the floor, as part of the air conditioning system, as well as providing space for power cabling.

Raised floors and other metal structures such as cable trays and ventilation ducts have caused many problems with "zinc whiskers in the past, and likely are still present in many data centers. This happens when microscopic metallic filaments form on metals such as zinc or tin that protect many metal structures and electronic components from corrosion. Maintenance on a raised floor or installing of cable etc. can dislodge the whiskers, which enter the airflow and may short circuit server components or power supplies, sometimes through a high current metal vapor "plasma arc. This phenomenon is not unique to data centers, and has also caused catastrophic failures of satellites and military hardware.[39]

To prevent "single points of failure, all elements of the electrical systems, including backup systems, are typically fully duplicated, and critical servers are connected to both the "A-side" and "B-side" power feeds. This arrangement is often made to achieve "N+1 redundancy in the systems. "Static transfer switches are sometimes used to ensure instantaneous switchover from one supply to the other in the event of a power failure.

Data cabling is typically routed through overhead "cable trays in modern data centers. But some["who?] are still recommending under raised floor cabling for security reasons and to consider the addition of cooling systems above the racks in case this enhancement is necessary. Smaller/less expensive data centers without raised flooring may use anti-static tiles for a flooring surface. Computer cabinets are often organized into a "hot aisle arrangement to maximize airflow efficiency.

Passive fire protection elements include the installation of "fire walls around the data center, so a fire can be restricted to a portion of the facility for a limited time in the event of the failure of the active fire protection systems. Fire wall penetrations into the server room, such as cable penetrations, coolant line penetrations and air ducts, must be provided with fire rated penetration assemblies, such as "fire stopping.

Physical security also plays a large role with data centers. Physical access to the site is usually restricted to selected personnel, with controls including a layered security system often starting with fencing, "bollards and "mantraps.[41] "Video camera surveillance and permanent "security guards are almost always present if the data center is large or contains sensitive information on any of the systems within. The use of finger print recognition "mantraps is starting to be commonplace.

Energy use is a central issue for data centers. Power draw for data centers ranges from a few kW for a rack of servers in a closet to several tens of MW for large facilities. Some facilities have power densities more than 100 times that of a typical office building.[42] For higher power density facilities, electricity costs are a dominant "operating expense and account for over 10% of the "total cost of ownership (TCO) of a data center.[43] By 2012 the cost of power for the data center is expected to exceed the cost of the original capital investment.[44]

In 2007 the entire "information and communication technologies or ICT sector was estimated to be responsible for roughly 2% of global "carbon emissions with data centers accounting for 14% of the ICT footprint.[45] The US EPA estimates that servers and data centers are responsible for up to 1.5% of the total US electricity consumption,[46] or roughly .5% of US GHG emissions,[47] for 2007. Given a business as usual scenario greenhouse gas emissions from data centers is projected to more than double from 2007 levels by 2020.[45]

Siting is one of the factors that affect the energy consumption and environmental effects of a datacenter. In areas where climate favors cooling and lots of renewable electricity is available the environmental effects will be more moderate. Thus countries with favorable conditions, such as: Canada,[48] Finland,[49] Sweden,[50] Norway [51] and Switzerland,[52] are trying to attract cloud computing data centers.

In an 18-month investigation by scholars at Rice University's Baker Institute for Public Policy in Houston and the Institute for Sustainable and Applied Infodynamics in Singapore, data center-related emissions will more than triple by 2020. [53]

The most commonly used metric to determine the energy efficiency of a data center is "power usage effectiveness, or PUE. This simple ratio is the total power entering the data center divided by the power used by the IT equipment.

Total facility power consists of power used by IT equipment plus any overhead power consumed by anything that is not considered a computing or data communication device (i.e. cooling, lighting, etc.). An ideal PUE is 1.0 for the hypothetical situation of zero overhead power. The average data center in the US has a PUE of 2.0,[46] meaning that the facility uses two watts of total power (overhead + IT equipment) for every watt delivered to IT equipment. State-of-the-art data center energy efficiency is estimated to be roughly 1.2.[54] Some large data center operators like "Microsoft and "Yahoo! have published projections of PUE for facilities in development; "Google publishes quarterly actual efficiency performance from data centers in operation.[55]

Often, the first step toward curbing energy use in a data center is to understand how energy is being used in the data center. Multiple types of analysis exist to measure data center energy use. Aspects measured include not just energy used by IT equipment itself, but also by the data center facility equipment, such as chillers and fans.[58]

Power is the largest recurring cost to the user of a data center.[59] A power and cooling analysis, also referred to as a thermal assessment, measures the relative temperatures in specific areas as well as the capacity of the cooling systems to handle specific ambient temperatures.[60] A power and cooling analysis can help to identify hot spots, over-cooled areas that can handle greater power use density, the breakpoint of equipment loading, the effectiveness of a raised-floor strategy, and optimal equipment positioning (such as AC units) to balance temperatures across the data center. Power cooling density is a measure of how much square footage the center can cool at maximum capacity.[61]

An energy efficiency analysis measures the energy use of data center IT and facilities equipment. A typical energy efficiency analysis measures factors such as a data center's power use effectiveness (PUE) against industry standards, identifies mechanical and electrical sources of inefficiency, and identifies air-management metrics.[62]

This type of analysis uses sophisticated tools and techniques to understand the unique thermal conditions present in each data center—predicting the temperature, airflow, and pressure behavior of a data center to assess performance and energy consumption, using numerical modeling.[63] By predicting the effects of these environmental conditions, CFD analysis in the data center can be used to predict the impact of high-density racks mixed with low-density racks[64] and the onward impact on cooling resources, poor infrastructure management practices and AC failure or AC shutdown for scheduled maintenance.

This water-cooled data center in the "Port of Strasbourg, France claims the attribute green.

Data centers use a lot of power, consumed by two main usages: the power required to run the actual equipment and then the power required to cool the equipment. The first category is addressed by designing computers and storage systems that are increasingly power-efficient.[2] To bring down cooling costs data center designers try to use natural ways to cool the equipment. Many data centers are located near good fiber connectivity, power grid connections and also people-concentrations to manage the equipment, but there are also circumstances where the data center can be miles away from the users and don't need a lot of local management. Examples of this are the 'mass' data centers like Google or Facebook: these DC's are built around many standardized servers and storage-arrays and the actual users of the systems are located all around the world. After the initial build of a data center staff numbers required to keep it running are often relatively low: especially data centers that provide mass-storage or computing power which don't need to be near population centers.Data centers in arctic locations where outside air provides all cooling are getting more popular as cooling and electricity are the two main variable cost components.[66]

The practice of cooling data centers is a topic of discussion. It is very difficult to reuse the heat which comes from air cooled data centers. For this reason, data center infrastructures are more often equipped with heat pumps. An alternative to heat pumps is the adoption of liquid cooling throughout a data center. Different liquid cooling techniques are mixed and matched to allow for a fully liquid cooled infrastructure which captures all heat in water. Different liquid technologies are categorised in 3 main groups, Indirect liquid cooling (water cooled racks), Direct liquid cooling (direct-to-chip cooling) and Total liquid cooling (complete immersion in liquid). This combination of technologies allows the creation of a "thermal cascade as part of "temperature chaining scenarios to create high temperature water outputs from the data center.

Some of the servers at the data center are used for running the basic Internet and "intranet services needed by internal users in the organization, e.g., e-mail servers, "proxy servers, and "DNS servers.

Network security elements are also usually deployed: "firewalls, "VPN "gateways, "intrusion detection systems, etc. Also common are monitoring systems for the network and some of the applications. Additional off site monitoring systems are also typical, in case of a failure of communications inside the data center.

"Data center infrastructure management (DCIM) is the integration of information technology (IT) and facility management disciplines to centralize monitoring, management and intelligent capacity planning of a data center's critical systems. Achieved through the implementation of specialized software, hardware and sensors, DCIM enables common, real-time monitoring and management platform for all interdependent systems across IT and facility infrastructures.

Depending on the type of implementation, DCIM products can help data center managers identify and eliminate sources of risk to increase availability of critical IT systems. DCIM products also can be used to identify interdependencies between facility and IT infrastructures to alert the facility manager to gaps in system redundancy, and provide dynamic, holistic benchmarks on power consumption and efficiency to measure the effectiveness of "green IT" initiatives.

It's important to measure and understand data center efficiency metrics. A lot of the discussion in this area has focused on energy issues, but other metrics beyond the PUE can give a more detailed picture of the data center operations. Server, storage, and staff utilization metrics can contribute to a more complete view of an enterprise data center. In many cases, disc capacity goes unused and in many instances the organizations run their servers at 20% utilization or less.[67] More effective automation tools can also improve the number of servers or virtual machines that a single admin can handle.

DCIM providers are increasingly linking with "computational fluid dynamics providers to predict complex airflow patterns in the data center. The CFD component is necessary to quantify the impact of planned future changes on cooling resilience, capacity and efficiency.[68]

Several parameters may limit the capacity of a data center. For long term usage, the main limitations will be available area, then available power. In the first stage of its life cycle, a data center will see its occupied space growing more rapidly than consumed energy. With constant densification of new IT technologies, the need in energy is going to become dominant, equaling then overcoming the need in area (second then third phase of cycle). The development and multiplication of connected objects, the needs in storage and data treatment lead to the necessity of data centers to grow more and more rapidly. It is therefore important to define a data center strategy before being cornered. The decision, conception and building cycle lasts several years. Therefore, it is imperative to initiate this strategic consideration when the data center reaches about 50% of its power capacity. Maximum occupation of a data center needs to be stabilized around 85%, be it in power or occupied area. Resources thus managed will allow a rotation zone for managing hardware replacement and will allow temporary cohabitation of old and new generations. In the case where this limit would be overcrossed durably, it would not be possible to proceed to material replacements, which would invariably lead to smothering the information system. The data center is a resource in its own right of the information system, with its own constraints of time and management (life span of 25 years), it therefore needs to be taken into consideration in the framework of the SI midterm planning (between 3 and 5 years).

The main purpose of a data center is running the IT systems applications that handle the core business and operational data of the organization. Such systems may be proprietary and developed internally by the organization, or bought from "enterprise software vendors. Such common applications are "ERP and "CRM systems.

Data centers are also used for off site backups. Companies may subscribe to backup services provided by a data center. This is often used in conjunction with "backup tapes. Backups can be taken off servers locally on to tapes. However, tapes stored on site pose a security threat and are also susceptible to fire and flooding. Larger companies may also send their backups off site for added security. This can be done by backing up to a data center. Encrypted backups can be sent over the Internet to another data center where they can be stored securely.

For quick deployment or "disaster recovery, several large hardware vendors have developed mobile/modular solutions that can be installed and made operational in very short time. Companies such as

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A modular data center connected to the power grid at a utility substation

According to data provided in the third quarter of 2013 by Synergy Research Group, "the scale of the wholesale colocation market in the United States is very significant relative to the retail market, with Q3 wholesale revenues reaching almost $700 million. "Digital Realty Trust is the wholesale market leader, followed at a distance by DuPont Fabros." Synergy Research also described the US colocation market as the most mature and well-developed in the world, based on revenue and the continued adoption of cloud infrastructure services.

^Clark, Jeffrey. "The Price of Data Center Availability—How much availability do you need?", Oct. 12, 2011, The Data Center Journal "Archived copy". Archived from the original on 2011-12-03. Retrieved 2012-02-08.